The objective of this study is to determine whether ultrasound exposure results in measurable alterations of cell membrane structures or membrane functions when applied to suspensions of mouse-derived peritoneal cells. The presence of ultrasound- induced cellular aberrations will be determined on purified macrophage populations using in vitro culture assays designed to detect alterations in cell surface determinants and functions characteristic of the macrophage. The broader objectives of this proposed study of bioeffects of pulsed ultrasound clinical diagnostic units are: o To enhance knowledge of the effects of ultrasound on the cell membrane through study of a variety of immunological endpoints. o To aid in assessing the risk (if any) of continued use of ultrasound in clinical diagnosis. Specific aims leading to these objectives are: o To identify and substantiate positive or negative results in the cases of a variety of immunological endpoints, some of which are previously unused in this field of research. o To determine, as far as possible, the mechanism of interaction of ultrasound with cells in suspension that give rise to any of the positive results. The following endpoints will be used: adherence and spreading; expression of Fc and C3b receptors; phagocytic index for sheep red blood cells; phagocytosis and intracellular killing of S. aureus; cytolytic activity of activated macrophages against murine tumor cells; ability to serve as accessory cells during in vitro mitogen stimulation of murine derived T-lymphocytes. During the study, we expect to accomplish: o Replicative assays by six methods utilizing nine sets of ultrasound exposure conditions that span a wide but typical range of exposure parameters. o Identification of endpoints that yield positive and negative results with customary statistical levels of confidence. o A delineation of the limits of exposure parameters that produce positive results (if any). o A set of experiments indicating the mechanism(s) of interaction of ultrasound with the cell membrane that result in immunological effects (if any).